From 4a777b6207b2f727b9a34be39a970b0c52b111ce Mon Sep 17 00:00:00 2001
From: KongQun Yang <kqyang@google.com>
Date: Wed, 4 Nov 2020 12:56:05 -0800
Subject: [PATCH] [HLS] Fixes attributes for DVS tracks

Always set AUTOSELECT=YES for DVS tracks and also exclude it from
standard AUTOSELECT and DEFAULT configuration logic.

Fixes #857.

Change-Id: Ie179d02390ff09f6e8c0b54892c1d6d32a3c38d6
---
 packager/hls/base/master_playlist.cc          | 16 +++++--
 packager/hls/base/master_playlist_unittest.cc | 45 +++++++++++++++++++
 packager/hls/base/media_playlist.h            |  9 ++++
 3 files changed, 66 insertions(+), 4 deletions(-)

diff --git a/packager/hls/base/master_playlist.cc b/packager/hls/base/master_playlist.cc
index e1c336cc80..b35ef4757e 100644
--- a/packager/hls/base/master_playlist.cc
+++ b/packager/hls/base/master_playlist.cc
@@ -366,12 +366,20 @@ void BuildMediaTags(
       bool is_default = false;
       bool is_autoselect = false;
 
-      const std::string language = playlist->language();
-      if (languages.find(language) == languages.end()) {
-        is_default = !language.empty() && language == default_language;
+      if (playlist->is_dvs()) {
+        // According to HLS Authoring Specification for Apple Devices
+        // https://developer.apple.com/documentation/http_live_streaming/hls_authoring_specification_for_apple_devices#overview
+        // section 2.13 If you provide DVS, the AUTOSELECT attribute MUST have
+        //              a value of "YES".
         is_autoselect = true;
+      } else {
+        const std::string language = playlist->language();
+        if (languages.find(language) == languages.end()) {
+          is_default = !language.empty() && language == default_language;
+          is_autoselect = true;
 
-        languages.insert(language);
+          languages.insert(language);
+        }
       }
 
       BuildMediaTag(*playlist, group_id, is_default, is_autoselect, base_url,
diff --git a/packager/hls/base/master_playlist_unittest.cc b/packager/hls/base/master_playlist_unittest.cc
index 9f0f0cf741..60fac6131f 100644
--- a/packager/hls/base/master_playlist_unittest.cc
+++ b/packager/hls/base/master_playlist_unittest.cc
@@ -523,6 +523,51 @@ TEST_F(MasterPlaylistTest, WriteMasterPlaylistVideoAndTextWithCharacteritics) {
   ASSERT_EQ(expected, actual);
 }
 
+TEST_F(MasterPlaylistTest, WriteMasterPlaylistVideoAndDvsAudio) {
+  // Video, sd.m3u8.
+  std::unique_ptr<MockMediaPlaylist> video =
+      CreateVideoPlaylist("sd.m3u8", "sdvideocodec", 300000, 200000);
+
+  // DVS Audio, dvs_eng.m3u8.
+  std::unique_ptr<MockMediaPlaylist> dvs_audio = CreateAudioPlaylist(
+      "dvs_eng.m3u8", "DVS english", "audiogroup", "audiocodec", "en", 2, 50000,
+      30000, kEC3JocComplexityZero, !kAC4IMSFlagEnabled, !kAC4CBIFlagEnabled);
+  dvs_audio->SetCharacteristicsForTesting(
+      std::vector<std::string>{"public.accessibility.describes-video"});
+
+  // Normal Audio, eng.m3u8.
+  std::unique_ptr<MockMediaPlaylist> audio = CreateAudioPlaylist(
+      "eng.m3u8", "english", "audiogroup", "audiocodec", "en", 2, 50000, 30000,
+      kEC3JocComplexityZero, !kAC4IMSFlagEnabled, !kAC4CBIFlagEnabled);
+
+  const char kBaseUrl[] = "http://playlists.org/";
+  EXPECT_TRUE(master_playlist_->WriteMasterPlaylist(
+      kBaseUrl, test_output_dir_, {video.get(), dvs_audio.get(), audio.get()}));
+
+  std::string actual;
+  ASSERT_TRUE(File::ReadFileToString(master_playlist_path_.c_str(), &actual));
+
+  const std::string expected =
+      "#EXTM3U\n"
+      "## Generated with https://github.com/google/shaka-packager version "
+      "test\n"
+      "\n"
+      "#EXT-X-MEDIA:TYPE=AUDIO,URI=\"http://playlists.org/dvs_eng.m3u8\","
+      "GROUP-ID=\"audiogroup\",LANGUAGE=\"en\",NAME=\"DVS english\","
+      "AUTOSELECT=YES,CHARACTERISTICS=\"public.accessibility.describes-video\","
+      "CHANNELS=\"2\"\n"
+      "#EXT-X-MEDIA:TYPE=AUDIO,URI=\"http://playlists.org/eng.m3u8\","
+      "GROUP-ID=\"audiogroup\",LANGUAGE=\"en\",NAME=\"english\","
+      "DEFAULT=YES,AUTOSELECT=YES,CHANNELS=\"2\"\n"
+      "\n"
+      "#EXT-X-STREAM-INF:BANDWIDTH=350000,AVERAGE-BANDWIDTH=230000,"
+      "CODECS=\"sdvideocodec,audiocodec\",RESOLUTION=800x600,"
+      "AUDIO=\"audiogroup\"\n"
+      "http://playlists.org/sd.m3u8\n";
+
+  ASSERT_EQ(expected, actual);
+}
+
 TEST_F(MasterPlaylistTest, WriteMasterPlaylistVideoAndTextGroups) {
   // Video, sd.m3u8.
   std::unique_ptr<MockMediaPlaylist> video =
diff --git a/packager/hls/base/media_playlist.h b/packager/hls/base/media_playlist.h
index 2b419b99c2..18d86494d4 100644
--- a/packager/hls/base/media_playlist.h
+++ b/packager/hls/base/media_playlist.h
@@ -221,6 +221,15 @@ class MediaPlaylist {
     return characteristics_;
   }
 
+  bool is_dvs() const {
+    // HLS Authoring Specification for Apple Devices
+    // https://developer.apple.com/documentation/http_live_streaming/hls_authoring_specification_for_apple_devices#overview
+    // Section 2.12.
+    const char DVS_CHARACTERISTICS[] = "public.accessibility.describes-video";
+    return characteristics_.size() == 1 &&
+           characteristics_[0] == DVS_CHARACTERISTICS;
+  }
+
  private:
   // Add a SegmentInfoEntry (#EXTINF).
   void AddSegmentInfoEntry(const std::string& segment_file_name,